Multi-Agent Architecture Adds Coordination Faster Than Capability

Adding a second agent creates a coordination problem before it creates a capability gain. Someone must define the assignment, preserve the relevant context, reconcile the result and decide whether another attempt is allowed. Those obligations exist even when the second agent produces nothing useful. The title describes that architectural asymmetry, not a universal measured growth rate: extra capability is possible, but it has to earn the machinery introduced to obtain it. Start with a working single-agent baseline. Split one part only when you can name the missing capability, state the boundary of the delegated task and verify the returned artifact. This article develops a coordination-budget table and a handoff contract for that decision. Its examples and numbers are hypothetical; they are not results from a benchmark or a client deployment. AI assisted the drafting and the conceptual cover. Define the result before multiplying the workers A system becomes more capable when it completes a useful job that the baseline cannot complete reliably, or achieves an agreed outcome within a better operating constraint. More messages, more tool calls and a longer final answer do not establish that improvement. The unit of value belongs to the user: a resolved support case, an accepted code change or a decision supported by the required evidence. Consider a support workflow that proposes an account adjustment. It reads a customer's request, retrieves the applicable policy and prepares a recommendation for an authorized operator. Success means the recommendation matches the relevant account facts and policy version, contains the required evidence and leaves the adjustment untouched until the authorized action. A persuasive explanation attached to the wrong account is a failure. The baseline could be one agent with retrieval and a narrowly defined set of read-only tools. It might already have several model calls, retries and deterministic checks. Single-agent does not mean one p